The use of hydrogels to form articles such as contact lenses is well known. It is further known to increase the oxygen permeability of hydrogels by adding silicone-containing monomers to the hydrogel formulations to produce silicone hydrogels.
Typically, it is desirable to increase the surface wettability of hydrogel and silicone hydrogel articles by coating the articles with a hydrophilic coating. Numerous hydrophilic coatings and methods for their application are known. For example, it is known to apply a coating to a silicone hydrogel lens using gas plasma. This coating method is disadvantageous in that it requires dehydration of the lens prior to application of the plasma treatment, which treatment must be carried out under vacuum conditions.
Alternatively, it is known to use solution- or solvent-based coatings to coat lenses. However, these coating methods, as does the plasma treatment, add steps to the lens manufacturing process and also result in the production of large quantities of waste. Further, application of a solution-based coating uniformly over a lens surface requires extremely precise process control.
Application of a coating onto a mold into which a lens material is dispensed also has been disclosed. However, this method has been successfully demonstrated only with non-silicone hydrogel materials. Therefore a need exists for a coating method for coating hydrogel and silicone hydrogel lenses that overcomes one or more of these disadvantages.